A transcriptome-based association study of growth, wood quality, and oleoresin traits in a slash pine breeding population.

Slash pine (Pinus elliottii Engelm.) is an important timber and resin species in the United States, China, Brazil and other countries. Understanding the genetic basis of these traits will accelerate its breeding progress. We carried out a genome-wide association study (GWAS), transcriptome-wide association study (TWAS) and weighted gene co-expression network analysis (WGCNA) for growth, wood quality, and oleoresin traits using 240 unrelated individuals from a Chinese slash pine breeding population. We developed high quality 53,229 single nucleotide polymorphisms (SNPs). Our analysis reveals three main results: (1) the Chinese breeding population can be divided into three genetic groups with a mean inbreeding coefficient of 0.137; (2) 32 SNPs significantly were associated with growth and oleoresin traits, accounting for the phenotypic variance ranging from 12.3% to 21.8% and from 10.6% to 16.7%, respectively; and (3) six genes encoding PeTLP, PeAP2/ERF, PePUP9, PeSLP, PeHSP, and PeOCT1 proteins were identified and validated by quantitative real time polymerase chain reaction for their association with growth and oleoresin traits. These results could be useful for tree breeding and functional studies in advanced slash pine breeding program.

MYB Transcription Factors and Its Regulation in Secondary Cell Wall Formation and Lignin Biosynthesis during Xylem Development.

The secondary wall is the main part of wood and is composed of cellulose, xylan, lignin, and small amounts of structural proteins and enzymes. Lignin molecules can interact directly or indirectly with cellulose, xylan and other polysaccharide molecules in the cell wall, increasing the mechanical strength and hydrophobicity of plant cells and tissues and facilitating the long-distance transportation of water in plants. MYBs (v-myb avian myeloblastosis viral oncogene homolog) belong to one of the largest superfamilies of transcription factors, the members of which regulate secondary cell-wall formation by promoting/inhibiting the biosynthesis of lignin, cellulose, and xylan. Among them, MYB46 and MYB83, which comprise the second layer of the main switch of secondary cell-wall biosynthesis, coordinate upstream and downstream secondary wall synthesis-related transcription factors. In addition, MYB transcription factors other than MYB46/83, as well as noncoding RNAs, hormones, and other factors, interact with one another to regulate the biosynthesis of the secondary wall. Here, we discuss the biosynthesis of secondary wall, classification and functions of MYB transcription factors and their regulation of lignin polymerization and secondary cell-wall formation during wood formation.

A systems genetics analysis in Eucalyptus reveals coordination of metabolic pathways associated with xylan modification in wood-forming tissues.

Acetyl- and methylglucuronic acid decorations of xylan, the dominant hemicellulose in secondary cell walls (SCWs) of woody dicots, affect its interaction with cellulose and lignin to determine SCW structure and extractability. Genes and pathways involved in these modifications may be targets for genetic engineering; however, little is known about the regulation of xylan modifications in woody plants. To address this, we assessed genetic and gene expression variation associated with xylan modification in developing xylem of Eucalyptus grandis × Eucalyptus urophylla interspecific hybrids. Expression quantitative trait locus (eQTL) mapping identified potential regulatory polymorphisms affecting gene expression modules associated with xylan modification. We identified 14 putative xylan modification genes that are members of five expression modules sharing seven trans-eQTL hotspots. The xylan modification genes are prevalent in two expression modules. The first comprises nucleotide sugar interconversion pathways supplying the essential precursors for cellulose and xylan biosynthesis. The second contains genes responsible for phenylalanine biosynthesis and S-adenosylmethionine biosynthesis required for glucuronic acid and monolignol methylation. Co-expression and co-regulation analyses also identified four metabolic sources of acetyl coenxyme A that appear to be transcriptionally coordinated with xylan modification. Our systems genetics analysis may provide new avenues for metabolic engineering to alter wood SCW biology for enhanced biomass processability.

Ethylene signaling induces gelatinous layers with typical features of tension wood in hybrid aspen.

The phytohormone ethylene impacts secondary stem growth in plants by stimulating cambial activity, xylem development and fiber over vessel formation. We report the effect of ethylene on secondary cell wall formation and the molecular connection between ethylene signaling and wood formation. We applied exogenous ethylene or its precursor 1-aminocyclopropane-1-carboxylic acid (ACC) to wild-type and ethylene-insensitive hybrid aspen trees (Populus tremula × tremuloides) and studied secondary cell wall anatomy, chemistry and ultrastructure. We furthermore analyzed the transcriptome (RNA Seq) after ACC application to wild-type and ethylene-insensitive trees. We demonstrate that ACC and ethylene induce gelatinous layers (G-layers) and alter the fiber cell wall cellulose microfibril angle. G-layers are tertiary wall layers rich in cellulose, typically found in tension wood of aspen trees. A vast majority of transcripts affected by ACC are downstream of ethylene perception and include a large number of transcription factors (TFs). Motif-analyses reveal potential connections between ethylene TFs (Ethylene Response Factors (ERFs), ETHYLENE INSENSITIVE 3/ETHYLENE INSENSITIVE3-LIKE1 (EIN3/EIL1)) and wood formation. G-layer formation upon ethylene application suggests that the increase in ethylene biosynthesis observed during tension wood formation is important for its formation. Ethylene-regulated TFs of the ERF and EIN3/EIL1 type could transmit the ethylene signal.

Thinning regimes and initial spacing for Eucalyptus plantations in Brazil

ABSTRACT This study focuses on the effects of different thinning regimes on clonal Eucalyptus plantations growth. Four different trials, planted in 1999 and located in Bahia and Espírito Santo States, were used. Aside from thinning, initial planting density, and post thinning fertilization application were also evaluated. Before canopy closure, and therefore before excessive competition between trees took place, it was found that stands planted under low densities (667 trees per hectare) presented a lower mortality proportion when compared to stand planted under higher densities (1111 trees per hectare). However, diameter growth prior to thinning operations was not statistically different between these two densities, presenting an overall mean of 4.9 cm/year. After canopy closure and the application of the thinning treatments, it was found that thinning regimes beginning early in the life of the stand and leaving a low number of residual trees presented the highest diameter and height growth. Unthinned treatments and thinning regimes late in the life of the stand (after 5.5 years), leaving a large number of residual trees presented the highest values of basal area production. The choice of the best thinning regime for Eucalyptus clonal material will vary according to the plantation objective.

Governance Options to Enhance Ecosystem Services in Cocoa, Soy, Tropical Timber and Palm Oil Value Chains.

Dutch policies have advocated sustainable commodity value chains, which have implications for the landscapes from which these commodities originate. This study examines governance and policy options for sustainability in terms of how ecosystem services are addressed in cocoa, soy, tropical timber and palm oil value chains with Dutch links. A range of policies addressing ecosystem services were identified, from market governance (certification, payments for ecosystem services) to multi-actor platforms (roundtables) and public governance (policies and regulations). An analysis of policy narratives and interviews identified if and how ecosystem services are addressed within value chains and policies; how the concept has been incorporated into value chain governance; and which governance options are available. The Dutch government was found to take a steering but indirect role in all the cases, primarily through supporting, financing, facilitating and partnering policies. Interventions mainly from end-of-chain stakeholders located in processing and consumption countries resulted in new market governance, notably voluntary sustainability standards. These have been successful in creating awareness of some ecosystem services and bringing stakeholders together. However, they have not fully addressed all ecosystem services or stakeholders, thus failing to increase the sustainability of value chains or of the landscapes of origin. We argue that chains sourced in tropical landscapes may be governed more effectively for sustainability if voluntary, market policy tools and governance arrangements have more integrated goals that take account of sourcing landscapes and impacts along the entire value chain. Given the international nature of these commodities. These findings have significance for debates on public-private approaches to value chain and landscape governance.

Rasgos morfológicos regenerativos en una comunidad de especies leñosas en un bosque seco tropical tumbesino / Regenerative morphological traits in a woody species community in Tumbesian tropical dry forest

ResumenEl estudio de rasgos morfológicos funcionales nos permite conocer muchos aspectos fundamentales de la dinámica de las comunidades vegetales en hábitats particulares y a nivel mundial, los rasgos morfológicos regenerativos cumplen un rol importante en la ecología e historia de las plantas por estar relacionados con la dispersión, germinación, colonización y establecimiento de las plántulas en determinados hábitas, sin embargo estos rasgos no han sido debidamente estudiados a nivel de toda una comunidad de especies leñosas en los bosques secos neotropicales. Los objetivos del presente estudio fueron; a) evaluar rasgos morfológicos funcionales en frutos, semillas y embriones de especies leñosas, b).- determinar que patrones morfológicos caracterizan a las semillas de la comunidad de especies leñosas y c) analizar la masa de la semillas con respecto a otros bosques tropicales. Entre el 2010 y 2014 se recolectaron en un bosque seco tumbesino ubicado al sur occidente del Ecuador frutos con semillas maduras de 79 especies pertenecientes a 42 árboles y 37 arbustos de 31 familias más representativas de los bosques secos tumbesinos. Se midió y describió un total de 18 rasgos morfológicos, 7 cuantitativos y 11 cualitativos en frutos, semillas y embriones. La descripción y análisis de los rasgos se realizaron en el Banco de Germoplasma de la UTPL. Los resultados mostraron gran heterogeneidad en los rasgos cuantitativos medidos, el tamaño de las semillas varió de 1.3 a 39 mm de largo x 0.6 a 25 mm de ancho, mientras que el promedio del largo de los embriones fue de 8.1 mm. El volumen, masa y número de semillas por fruto fueron los rasgos que presentaron mayor variabilidad. La mayoría de especies de bosque seco se caracterizaron por presentar frutos secos dispersados por animales, con semillas ovaladas sin areola, lisas y de testa dura. Encontramos solamente seis tipos de embriones en las semillas, el 40 % de las especies se caracterizó por presentar embriones invertidos bien desarrollados con cotiledones grandes y gruesos que ocupan todo el interior de la semillas y cumplen la función de almacenamiento de reservas nutritivas. En conclusión, existe gran variabilidad y heterogeneidad en los rasgos morfológicos de las semillas de especies leñosas del bosque seco, lo que les permitiría tener un amplio rango de mecanismos y comportamiento para soportar condiciones de estrés ambiental en zonas áridas. Las implicaciones ecológicas que podrían tener los rasgos que caraterizan a los frutos, semillas y embriones de la comunidad de especies leñosas posiblemente les permitan estar mejor preparadas para soportar los cambios climáticos globales pronosticados para los próximos años.

AbstractThe study of functional morphological traits enables us to know fundamental aspects of the dynamics of plant communities in local and global habitats. Regenerative morphological traits play an important role in defining plant history and ecological behavior. Seed and fruit characteristics determine to a large extent the patterns for dispersal, germination, establishment and seedling recruitment a given species exhibits on its natural habitat. Despite their prominent role, seed and fruit traits have been poorly studied at the community level of woody plant species in neo-tropical dry forests. In the present study we aimed at i) evaluate the functional role of morphological traits of seeds, fruits and embryo in woody plant species; ii) determine which are the morphological patterns present in seeds collected from the community of woody species that occur in neo-tropical dry forests; and iii) compare woody plant species seed mass values comparatively between neo-tropical dry and tropical forests. To do so, mature seeds were collected from 79 plant species that occur in the Tumbesian forest of Southwest Ecuador. The studied species included the 42 and 37 most representative tree and shrubbery species of the Tumbesian forest respectively. A total of 18 morphological traits (seven quantitative and 11 qualitative) were measured and evaluated in the seeds, fruits and embryos of the selected species, and we compared the seeds mass with other forest types. Our results showed a huge heterogeneity among traits values in the studied species. Seed mass, volume and number were the traits that vary the most at the community level, i.e. seed length ranged from 1.3 to 39 mm, and seed width from 0.6 to 25 mm. Only six embryo types were found among the 79 plant species. In 40 % of the cases, fully developed inverted embryos with large and thick cotyledons to store considerable amount of nutrients were recorded. We concluded that highly variable and functionally complementary morphological traits occur among the studied woody plants of the Tumbesian dry forest. The latter favors a plethora of behavioral mechanisms to coexist among woody species of the dry forest in response to the environmental stress that is typical of arid areas. Rev. Biol. Trop. 64 (2): 859-873. Epub 2016 June 01.

Quantitative proteomics reveals protein profiles underlying major transitions in aspen wood development.

BACKGROUND: Wood development is of outstanding interest both to basic research and industry due to the associated cellulose and lignin biomass production. Efforts to elucidate wood formation (which is essential for numerous aspects of both pure and applied plant science) have been made using transcriptomic analyses and/or low-resolution sampling. However, transcriptomic data do not correlate perfectly with levels of expressed proteins due to effects of post-translational modifications and variations in turnover rates. In addition, high-resolution analysis is needed to characterize key transitions. In order to identify protein profiles across the developmental region of wood formation, an in-depth and tissue specific sampling was performed. RESULTS: We examined protein profiles, using an ultra-performance liquid chromatography/quadrupole time of flight mass spectrometry system, in high-resolution tangential sections spanning all wood development zones in Populus tremula from undifferentiated cambium to mature phloem and xylem, including cell expansion and cell death zones. In total, we analyzed 482 sections, 20-160 µm thick, from four 47-year-old trees growing wild in Sweden. We obtained high quality expression profiles for 3,082 proteins exhibiting consistency across the replicates, considering that the trees were growing in an uncontrolled environment. A combination of Principal Component Analysis (PCA), Orthogonal Projections to Latent Structures (OPLS) modeling and an enhanced stepwise linear modeling approach identified several major transitions in global protein expression profiles, pinpointing (for example) locations of the cambial division leading to phloem and xylem cells, and secondary cell wall formation zones. We also identified key proteins and associated pathways underlying these developmental landmarks. For example, many of the lignocellulosic related proteins were upregulated in the expansion to the early developmental xylem zone, and for laccases with a rapid decrease in early xylem zones. We observed upregulation of two forms of xylem cysteine protease (Potri.002G005700.1 and Potri.005G256000.2; Pt-XCP2.1) in early xylem and their downregulation in late maturing xylem. Our data also show that Pt-KOR1.3 (Potri.003G151700.2) exhibits an expression pattern that supports the hypothesis put forward in previous studies that this is a key xyloglucanase involved in cellulose biosynthesis in primary cell walls and reduction of cellulose crystallinity in secondary walls. CONCLUSION: Our novel multivariate approach highlights important processes and provides confirmatory insights into the molecular foundations of wood development.

Inter-site variation in allometry and wood density of Goupia glabra Aubl. in Amazonia / Variação entre-sítios na alometria e densidade da madeira de Goupia glabra Aubl. na Amazônia

Abstract The present study aims to compare the allometry and wood density of Goupia glabra Aubl. (Goupiaceae) in two different terra-firme sites in Amazonian forest. A total of 65 trees ≥ 10 cm DBH was sampled in both sites, with 39 trees in Nova Olinda do Norte (NOlinda, near the Amazon River) and 29 trees in Apuí (near the southern edge of the Amazon forest). Except for the relationship between DBH (diameter at breast height) and Ht (total height), allometric relationships for G.glabra differed significantly between sites. Apuí had lower intercept and greater slope for log10 (DBH) versus log10 (Hs – stem height), and, conversely, greater intercept and lower slope for log10 (DBH) versus log10 (Ch – crown height). The slope differed significantly between the sites for DBH versus Cd (crown diameter), with greater slope found for NOlinda. Mean basic wood density in Apuí was 8.8% lower than in NOlinda. Our findings highlight the variation in adaptive strategy of G. glabra due to environmental differences between sites. This is probably because of different canopy-understory light gradients, which result in differentiation of resource allocation between vertical and horizontal growth, which, in turn, affects mechanical support related to wood density. We also hypothesize that differences in soil fertility and disturbance regimes between sites may act concomitantly with light.

Resumo O presente estudo tem como objetivo comparar a alometria e a densidade da madeira de Goupia glabra em dois diferentes sítios de floresta de terra firme na Amazonia. Um total de 65 árvores com DAP ≥ 10 cm foi amostrado em ambos os sítios, sendo 39 árvores em Nova Olinda do Norte (NOlinda, próximo ao rio Amazonas) e 29 em Apuí (próximo à borda sul da Amazônia). Exceto para a relação entre o DBH (diâmetro a altura do peito) e a Ht (altura total), as relações alométricas para G. glabra diferiu significativamente entre os sítios. Apuí apresentou menor intercepto e maior inclinação para a relação log10 (DBH) versus log10 (Hs – altura do fuste) e, ao contrário, maior intercepto e menor inclinação para log10 (DBH) versus log10 (Ch – altura da copa). A inclinação diferiu significativamente entre os sítios para DBH versus Cd (diâmetro da copa), com maior inclinação encontrada para NOlinda. A densidade básica média da madeira in Apuí foi 8.8% menor do que em NOlinda. Os resultados deste estudo destacam a variação na estratégia adaptativa de G. glabra devido às diferenças ambientais entre os sítios. Isto é provavelmente consequência dos diferentes gradientes de luz o que resulta na diferenciação na alocação de recursos entre o crescimento vertical e horizontal o que, por sua vez, afeta o suporte mecânico relacionado à densidade da madeira. Nós também levantamos a hipótese de que as diferenças em termos de fertilidade e regimes de distúrbios entre os sítios podem agir concomitantemente com o regime de luz.

Growth responses of Scots pine to climatic factors on reclaimed oil shale mined land.

Afforestation on reclaimed mining areas has high ecological and economic importance. However, ecosystems established on post-mining substrate can become vulnerable due to climate variability. We used tree-ring data and dendrochronological techniques to study the relationship between climate variables and annual growth of Scots pine (Pinus sylvestris L.) growing on reclaimed open cast oil shale mining areas in Northeast Estonia. Chronologies for trees of different age classes (50, 40, 30) were developed. Pearson's correlation analysis between radial growth indices and monthly climate variables revealed that precipitation in June-July and higher mean temperatures in spring season enhanced radial growth of pine plantations, while higher than average temperatures in summer months inhibited wood production. Sensitivity of radial increment to climatic factors on post-mining soils was not homogenous among the studied populations. Older trees growing on more developed soils were more sensitive to precipitation deficit in summer, while growth indices of two other stand groups (young and middle-aged) were highly correlated to temperature. High mean temperatures in August were negatively related to annual wood production in all trees, while trees in the youngest stands benefited from warmer temperatures in January. As a response to thinning, mean annual basal area increment increased up to 50 %. By managing tree competition in the closed-canopy stands, through the thinning activities, tree sensitivity and response to climate could be manipulated.

Composición de especies leñosas en comunidades invadidas en montañas del centro de Argentina: su relación con factores ambientales locales

Woody species composition in invaded communities from mountains of central Argentina: their relations with local environmental factors. Invasions by exotic woody species are threatening ecosystem functions worldwide. The spread and subsequent replacement of native forest by exotic dominated stands is particularly evident nearby urban centers were exotic propagule pressure is highest. Yet, there is a lack of information on the environmental factors that underlie these replacements. In this study we addressed the following questions: (1) is there a local spatial segregation between the dominant native and exotic woody species? and (2) if this local segregation does exist, is it driven by environmental features?. For this, in 2010 we established 31 plots distributed along 16 sampling sites where we surveyed the composition and abundance of all woody species with a basal diameter ≥ 5cm. To characterize the environment of each plot, we measured the topographic position (slope, exposure) and different properties such as soil physics (bulk density, soil impedance), structure (soil deep, texture) and chemical characteristics (pH, nutrient and water content). Through a cluster analysis we were able to identify five different woody communities in coexistence: (1) Woodlands dominated by the exotic Ligustrum lucidum; (2) Mixed woodlands dominated by the native Lithraea molleoides and the exotic Celtis australis; (3) Scrublands dominated by the native Condalia buxifolia; (4) Scrublands dominated by the exotic Cotoneaster glaucophyllus, and (5) Scrubby grasslands with the exotic Pyracantha angustifolia. These communities were all associated with different local topographic and edaphic features. The environmental segregation among the identified communities suggests that woody invaders have the potential to colonize almost all the environments of the study site (though varying in the identity of the dominant exotic species). The observed patterns, even being restricted to a single well invaded area of mountain Chaco, may posit the spread of woody invaders towards native communities in the region.

En todo el mundo, las invasiones de especies leñosas exóticas están amenazando las funciones ecosistémicas. La dispersión y el subsecuente reemplazo de bosques de especies nativas por comunidades dominadas por exóticas es evidente, particularmente, en proximidad a centros urbanos donde la presión de propágulos de especies exóticas es alta. Sin embargo, existe una falta de información sobre los factores ambientales que subyacen este reemplazo. En este estudio nos propusimos responder las siguientes preguntas: (1) ¿se observa una segregación espacial a escala local entre especies leñosas exóticas y/o nativas dominantes?, y (2) si existe esa segregación, ¿está asociada a variables ambientales? En el 2010 se establecieron 31 parcelas distribuidas en 16 laderas en los bosques Chaqueños de las Sierras de Córdoba, en Argentina central. En cada uno de los sitios de muestreo se relevó la composición y abundancia de todas las especies leñosas con un diámetro a la altura de la base superior a 5cm. Para caracterizar el ambiente en cada una de las parcelas medimos la posición topográfica (pendiente y orientación) y algunas propiedades asociadas con la física (densidad aparente y compactación), estructura (profundidad y textura) y con la química (pH y el contenido de nutrientes y agua) del suelo. A través, de un análisis jerárquico de agrupamiento, se identificaron cinco comunidades de leñosas coexistiendo: (1) Bosques dominados por Ligustrum lucidum, (2) Bosques mixtos dominados por Lithraea molleoides y Celtis australis, (3) Matorrales de Condalia buxifolia, (4) Matorrales de Cotoneaster glaucophyllus, y (5) Pajonales con emergentes de Pyracantha angustifolia. Estas comunidades se asociaron diferencialmente a las variables topográficas y edáficas locales. La segregación ambiental observada sugiere que las especies invasoras tienen una capacidad potencial para colonizar casi todos los ambientes en el área de estudio (variando la identidad de la invasora). En conjunto, los patrones descritos, aunque circunscriptos a un área de Chaco Serrano con un avanzado grado de invasión, plantearían un escenario de posible expansión de las leñosas exóticas sobre las comunidades nativas.

Proteomic analysis during ontogenesis of secondary xylem in maritime pine.

Secondary xylem (wood) is formed through an intricate biological process that results in a highly variable final product. Studies have focused on understanding the molecular events for wood formation in conifers. In this process environmental, ontogenic and genetic factors influence variation in wood characteristics, including anatomical, chemical and physical properties. The main objective of this study was to analyse the ageing (ontogenic) effect on protein accumulation in wood-forming tissues along a cambial age (CA) gradient, ranging from juvenile wood (JW) sampled at the top of the tree, to mature wood (MW) sampled at the bottom of the tree. A total of 62 proteins whose accumulation varied by at least 1.5-fold according to CA were selected and identified by ESI-MS/MS; 30 of these were more abundant in MW and 32 were more abundant in JW. Consistent with earlier findings, our results show that JW is a tissue characterized by a high energy demand with the accumulation of gene products involved in energy, protein fate and cellular transport, while proteins identified in MW (heat shock response, oxygen and radical detoxification, and the S-adenosyl methionine cycle) support the idea that this tissue undergoes extended cell-wall thickening and a delay of programmed cell death.

RNA isolation from loquat and other recalcitrant woody plants with high quality and yield.

RNA isolation is difficult in plants that contain large amounts of polysaccharides and polyphenol compounds. To date, no commercial kit has been developed for the isolation of high-quality RNA from tissues with these characteristics, especially for fruit. The common protocols for RNA isolation are tedious and usually result in poor yields when applied to recalcitrant plant tissues. Here an efficient RNA isolation protocol based on cetyltrimethylammonium bromide (CTAB) and two successive precipitations with 10 M lithium chloride (LiCl) was developed specifically for loquat fruits, but it was proved to work efficiently in other tissues of loquat and woody plants. The RNA isolated by this improved protocol was not only of high purity and integrity (A260/A280 ratios ranged from 1.90 to 2.04 and A260/A230 ratios were>2.0) but also of high yield (up to 720 µg on average [coefficient of variation=21%] total RNA per gram fresh tissue). The protocol was tested on loquat fruit (different stages of development, postharvest, ripening, and bruising), leaf, root, flower, stem, and bud; quince fruit and root; grapevine cells in liquid culture; and rose petals. The RNA obtained with this method is amenable to enzymatic treatments and can be efficiently applied for research on gene characterization, expression, and function.

A genome-wide screen for ethylene-induced ethylene response factors (ERFs) in hybrid aspen stem identifies ERF genes that modify stem growth and wood properties.

Ethylene Response Factors (ERFs) are a large family of transcription factors that mediate responses to ethylene. Ethylene affects many aspects of wood development and is involved in tension wood formation. Thus ERFs could be key players connecting ethylene action to wood development. We identified 170 gene models encoding ERFs in the Populus trichocarpa genome. The transcriptional responses of ERF genes to ethylene treatments were determined in stem tissues of hybrid aspen (Populus tremula × tremuloides) by qPCR. Selected ethylene-responsive ERFs were overexpressed in wood-forming tissues and characterized for growth and wood chemotypes by FT-IR. Fifty ERFs in Populus showed more than five-fold increased transcript accumulation in response to ethylene treatments. Twenty-six ERFs were selected for further analyses. A majority of these were induced during tension wood formation. Overexpression of ERFs 18, 21, 30, 85 and 139 in wood-forming tissues of hybrid aspen modified the wood chemotype. Moreover, overexpression of ERF139 caused a dwarf-phenotype with altered wood development, and overexpression of ERF18, 34 and 35 slightly increased stem diameter. We identified ethylene-induced ERFs that respond to tension wood formation, and modify wood formation when overexpressed. This provides support for their role in ethylene-mediated regulation of wood development.

Mineral nutrition and elevated [CO(2)] interact to modify δ(13)C, an index of gas exchange, in Norway spruce.

The effects of the past century's increase in atmospheric CO2 concentration ([CO2]) have been recorded in the stable carbon isotope composition (δ(13)C) of the annual growth rings of trees. The isotope record frequently shows increases in photosynthetic CO2 uptake relative to stomatal conductance, which estimates the CO2 concentration gradient across the stomata (ca - ci). This variable, which is one control over the net photosynthetic rate, has been suggested as a homeostatic gas-exchange set point that is easy to estimate from δ(13)C and [CO2]. However, in high-latitude conifer forests, the literature is mixed; some studies show increases in (ca - ci) and others show homeostasis. Here we present leaf and tree-ring δ(13)C data from a controlled experiment that tested factorial combinations of elevated [CO2] (365 and 700 ∝mol mol(-1)) and fertilization on mature Norway spruce (Picea abies (L.) Karst.) trees in northern Sweden. We found first that the leaf carbon pool was contaminated by the current photosynthate in the older leaf cohorts. This is the reverse of the common observation that older photosynthate reserves can be used to produce new tissue; here the older tissue contains recent photosynthate. We found that the tree-ring data lack such contamination and in any case they better integrate over the canopy and the growing season than do leaves. In the second and third years of treatment, elevated [CO2] alone increased (ca - ci) by 38%; when combined with fertilization, it increased (ca - ci) by 60%. The results of this study support the idea that annual rings provide a clearer isotopic signal than do foliage age-classes. The tree-ring data show that inferred (ca - ci) depends not only on [CO2], but also on mineral-nutrient status. The differences in (ca - ci) are sufficiently large to account for the treatment-induced increase in wood-volume production in these stands.

Reprogramming of gene expression during compression wood formation in pine: coordinated modulation of S-adenosylmethionine, lignin and lignan related genes.

BACKGROUND: Transcript profiling of differentiating secondary xylem has allowed us to draw a general picture of the genes involved in wood formation. However, our knowledge is still limited about the regulatory mechanisms that coordinate and modulate the different pathways providing substrates during xylogenesis. The development of compression wood in conifers constitutes an exceptional model for these studies. Although differential expression of a few genes in differentiating compression wood compared to normal or opposite wood has been reported, the broad range of features that distinguish this reaction wood suggest that the expression of a larger set of genes would be modified. RESULTS: By combining the construction of different cDNA libraries with microarray analyses we have identified a total of 496 genes in maritime pine (Pinus pinaster, Ait.) that change in expression during differentiation of compression wood (331 up-regulated and 165 down-regulated compared to opposite wood). Samples from different provenances collected in different years and geographic locations were integrated into the analyses to mitigate the effects of multiple sources of variability. This strategy allowed us to define a group of genes that are consistently associated with compression wood formation. Correlating with the deposition of a thicker secondary cell wall that characterizes compression wood development, the expression of a number of genes involved in synthesis of cellulose, hemicellulose, lignin and lignans was up-regulated. Further analysis of a set of these genes involved in S-adenosylmethionine metabolism, ammonium recycling, and lignin and lignans biosynthesis showed changes in expression levels in parallel to the levels of lignin accumulation in cells undergoing xylogenesis in vivo and in vitro. CONCLUSIONS: The comparative transcriptomic analysis reported here have revealed a broad spectrum of coordinated transcriptional modulation of genes involved in biosynthesis of different cell wall polymers associated with within-tree variations in pine wood structure and composition. In particular, we demonstrate the coordinated modulation at transcriptional level of a gene set involved in S-adenosylmethionine synthesis and ammonium assimilation with increased demand for coniferyl alcohol for lignin and lignan synthesis, enabling a better understanding of the metabolic requirements in cells undergoing lignification.

Growth ring analysis of fossil coniferous woods from early cretaceous of Araripe Basin (Brazil)

Growth ring analysis on silicified coniferous woods from the Missão Velha Formation (Araripe Basin - Brazil) has yielded important information about periodicity of wood production during the Early Cretaceous in the equatorial belt. Despite warm temperatures, dendrological data indicate that the climate was characterized by cyclical alternation of dry and rainy periods influenced by cyclical precipitations, typical of tropical wet and dry or savanna climate. The abundance of false growth rings can be attributed to both occasional droughts and arthropod damage. The present climate data agree with palaeoclimatic models that inferred summer-wet biomes for the Late Jurassic/Early Cretaceous boundary in the southern equatorial belt.

A partir de análise de anéis de crescimento em lenhos de coníferas silicificadas provenientes da Formação Missão Velha(Bacia do Araripe - Brasil), obteve-se importantes informações a respeito da periodicidade de produção lenhosa duranteo início do Cretáceo, na região do equador. Apesar das estimativas de temperatura apresentarem-se elevadas, os dados dendrológicos indicam que o clima foi caracterizado pela alternância cíclica de períodos secos e chuvosos, influenciado por precipitações periódicas, típico das condições atuais de climatropical úmido e seco ou savana. A abundância de falsosanéis de crescimento pode ser atribuída tanto a secas ocasionais quanto a danos causados por artrópodes. Os dados paleoclimáticos aqui obtidos corroboram com modelos paleoclimáticos que inferem a ocorrência de um bioma de verões úmidos para o limite Neojurássico/Eocretáceo ao sul do equador.

Maturation stress generation in poplar tension wood studied by synchrotron radiation microdiffraction.

Tension wood is widespread in the organs of woody plants. During its formation, it generates a large tensile mechanical stress called maturation stress. Maturation stress performs essential biomechanical functions such as optimizing the mechanical resistance of the stem, performing adaptive movements, and ensuring the long-term stability of growing plants. Although various hypotheses have recently been proposed, the mechanism generating maturation stress is not yet fully understood. In order to discriminate between these hypotheses, we investigated structural changes in cellulose microfibrils along sequences of xylem cell differentiation in tension and normal wood of poplar (Populus deltoides × Populus trichocarpa 'I45-51'). Synchrotron radiation microdiffraction was used to measure the evolution of the angle and lattice spacing of crystalline cellulose associated with the deposition of successive cell wall layers. Profiles of normal and tension wood were very similar in early development stages corresponding to the formation of the S1 layer and the outer part of the S2 layer. Subsequent layers were found with a lower microfibril angle (MFA), corresponding to the inner part of the S2 layer of normal wood (MFA approximately 10°) and the G layer of tension wood (MFA approximately 0°). In tension wood only, this steep decrease in MFA occurred together with an increase in cellulose lattice spacing. The relative increase in lattice spacing was found close to the usual value of maturation strains. Analysis showed that this increase in lattice spacing is at least partly due to mechanical stress induced in cellulose microfibrils soon after their deposition, suggesting that the G layer directly generates and supports the tensile maturation stress in poplar tension wood.

The poplar MYB transcription factors, PtrMYB3 and PtrMYB20, are involved in the regulation of secondary wall biosynthesis.

Dicot wood is mainly composed of cellulose, xylan and lignin, and its formation requires the coordinated regulation of their biosynthesis. In this report, we demonstrate that the poplar wood-associated MYB transcriptional activators, PtrMYB3 and PtrMYB20, activate the biosynthetic pathways of cellulose, xylan and lignin when overexpressed in Arabidopsis and they are also able to activate the promoter activities of poplar wood biosynthetic genes. We also show that PtrMYB3 and PtrMYB20 are functional orthologs of Arabidopsis MYB46 and MYB83, and their expression is directly activated by poplar PtrWND2, suggesting their involvement in the regulation of wood formation in poplar.

Ethylene evolution changes in tilted Fraxinus mandshurica Rupr. var. japonica maxim. seedlings in relation to tension wood formation.

The effects of ethylene on tension wood formation were studied in 3-year-old Fraxinus mandshurica Rupr. var. japonica Maxim. seedlings in two separate experiments. In experiment 1, ethylene evolution of buds and stems was measured using gas chromatography after 0, 2, 4, 7, 14, and 21 d of treatment; in experiment 2, both aminoethoxyvinylglycine (AVG) and AgNO3 were applied to the horizontally-placed stems, and the cell numbers on sites of applications were measured after 40 d. Ethylene evolution from buds was found to be much greater in tilted seedlings than in upright ones. The cell numbers of wood fibers in shoots and 1-year-old stems were reduced in treatments with 12.5 x 10(-7)micromol/L AVG, 12.5 x 10(-8)micromol/L AVG, and 11.8 x 10(-8)micromol/L AgNO3; whereas the horizontal and vertical diameters were reduced by treatment of 12.5 x 10(-7)micromol/L AVG. Ethylene evolutions of shoots and 1-year-old stems were inhibited greatly in comparison with the control by applying 12.5 x 10(-7)micromol/L AVG. The formation of a gelatinous layer of wood fibers was affected by neither AVG nor AgNO3 application. These results suggest that ethylene regulates the quantity of wood production, but does not affect G-layer formation in F. mandshurica Rupr. var. japonica Maxim. seedlings.